Restoration of an Eroded River Channel

Amenity Water Management Ltd

Restoration of an Eroded River Channel

This stretch of the River Tillingbourne runs through an on-line lake which fed a now converted mill. Over time wave lap erosion ably assisted by crayfish had left the channel over widened, shallow, unattractive and unhealthy.

AWM restored the channel to it's former width and sinuosity with a revetment using natural stone retained by a galvanised mesh panel and fence posts. Pre-planted and established coir rolls containing aquatic marginal plants were set on top of the stone.

The stone protects the bank while still providing good habitat and the roots from the planting will bind the stone and the bank together producing a sustainable solution to the problem.

Formerly the river entered the property and the flow was encouraged to split either side of one of two islands by means of timber boards set in the channel. The AWM design concentrated on one restored channel using the entire flow of water damming off the old back channel and encouraging that part of the lake to silt up and become wetland habitat colonised by reeds.

Looking downstream from the same position the over wide channel ran in a straight line down into the lake between the islands. The mean depth of water was 50-75mm.

The straight channel from the other bank as it was looking downstream to the mill. You can see the ongoing extent of the erosion.

The new channel looking upstream at where the diversion boards were. Note the stone filled gabion weirs allowing water to use the old channels behind the islands in flood conditions.

AWM access the site through the neighbouring Thames Water pumping works using a temporary timber matt road.

Looking downstream at the mill the new channel now has a more natural sinuosity with increased depth, improved flow and greatly enhanced aesthetic appeal. All of which is appreciated not least by the resident swan!